Physical properties of a Chernozemic clay loam soil under long-term conventional tillage and no-till

Abstract

Conservation tillage practices such as no-till (NT) and conventional tillage (CT) with a heavy-duty cultivator can influence the physical properties of soils. This study was conducted to determine the effect of 24 yr of NT versus CT on the physical properties of a clay loam soil in southern Alberta. Physical properties quantified were bulk density (BD), mean weight diameter (MWD), plant-available water-holding capacity (PAWHC), saturated hydraulic conductivity (Ksat), soil water characteristic [θ(ψ)] and unsaturated hydraulic conductivity [K(ψ)] relationships, and pore-size distribution (PSD). Bulk soil samples and small soil cores (5-cm depth increments to 20 cm) were taken from CT and NT fields in 1992, and tension infiltrometer measurements were made in 1994. The results from this study are reported as general trends for the tillage fields. Statistical probability levels are not reported because of the unreplicated nature of the experiment, the limited number of sampling locations within each tillage field, and to a lesser extent, the different sampling times for CT and NT in 1992. Plant-available water-holding capacity was higher for the CT field (14.3%) than the NT field (10.8%), and a greater amount of water was held at a given water potential (−1500 to −1.5 kPa) for the former, indicating a higher potential for soil water conservation under conventional tillage. Geometric mean Ksat values (small soil cores) were higher for the NT field (18.20 × 10−6 m s−1) than the CT field (1.74 × 10−6 m s−1). The K(ψ) values (small soil cores) between −10 and −2 kPa were higher for the CT field than the NT field at the 0- to 5-cm, 10- to 15-cm and 15- to 20-cm depths, but values were higher for the NT field at the 5- to 10-cm depth. Near-saturated K(ψ) values (−1.5 to −0.3 kPa) of the surface soil, as derived from tension infiltration measurements in 1994, were higher for the CT field (2.43 × 10−7 m s−1) than for the NT field (6.09 × 10−8 m s−1). There was a greater percentage volume of larger pores (30–40, 40–67, 67–200, >200 µm) for the NT field than for the CT field, and there was a lower percentage volume of smaller pores (0.2–0.6, 0.6–4 µm) for the CT field than for the NT field. Differences in certain soil physical properties between CT and NT fields may be related to the lag time between the most recent tillage event and sampling for the CT field. Key words: Conservation tillage, heavy-duty cultivator, physical attributes, soil water, hydraulic conductivity, porosity